A consumer watchdog launched an investigation into secondhand car sales as it was reported that thousands of motorists had unwittingly bought former rental vehicles from official dealerships.
The Office of Fair Trading (OFT) opened the study into the £35 billion second-hand car market after nearly 70,000 consumers complained in the last year alone.
Issues ranged from concerns around defective vehicles, services and potentially misleading selling.
The Telegraph reported some buyers paid over the odds after being told their vehicles had "one previous owner" when in fact they had been rented out to many drivers.
Norman Baker, the Liberal Democrat transport spokesman, called for regulations to be tightened.
He told the paper: "This is shady trading in an attempt to get higher prices for vehicles that have been driven by many people, possibly carelessly.
"Every ex-rental vehicle should have to be clearly labelled. We would like to see trading standards bring a test case to see whether this activity could be in breach of the consumer protection regulations."
Last year, more than 68,000 consumers complained to Consumer Direct about issues with second-hand car sales.
The second-hand car market is large, with sales of approximately £35 billion in 2008, the OFT said.
A spokesman said the financial cost of car clocking alone is estimated to be £100 million per year.
The OFT launched the study to discover why the level of consumer complaints was so high and consider whether existing consumer protection legislation was strong enough.
The OFT study, launched in the summer, is focusing on sales by dealers rather than private sales between individuals.Reuse content